1. Field of the Invention
The present invention relates to a method of magnetically transferring magnetic information signals held in a master medium to a slave medium.
2. Description of the Prior Art
The magnetic transfer method is one for magnetically transferring magnetic patterns corresponding to magnetic information (for example, servo signals) held in a master medium to a slave medium by applying transferring magnetic field in a state where the master medium and the slave medium are in close contact with each other. This magnetic transfer method is disclosed, for example, in Japanese Unexamined Patent Publication Nos. 63(1988)-183623, 10(1998)-40544, 10(1998)-269566 and the like.
However, if an adhering substance exists between the master medium and the slave medium in magnetically transferring the magnetic pattern from the master medium to the slave medium (during magnetic transfer), a space is created between the master medium and the slave medium in the vicinity of the adhering substance to cause an insufficient contact, and hence an area is created, where no magnetic transfer is executed. If such an area is created, where no magnetic transfer is executed, the magnetic information is not transferred at this area, and signal missing occurs in the magnetic information transferred to the slave medium. Thus, the signal quality is lowered. When the recorded signals are servo signals, a satisfactory tracking function cannot be obtained, and reliability of reproducing the information signals is lowered.
Specifically, as schematically shown in FIG. 3, during magnetic transfer, an information bearing plane of a master medium 3 and a magnetic recording surface of a slave medium 2 are made to contact each other, and by pressing a back of the slave medium 2 against the information bearing plane of the master medium 3 with a pressing support member 5, the information bearing plane and the magnetic recording surface are made to be in close contact with each other. In this state, a transferring magnetic field is applied to the master medium 3 and the slave medium 2 by magnetic field generating means (not shown), and information such as servo signals is magnetically transferred and recorded onto the slave medium 2 from the master medium 3. However, if an adhering substance P (particle) is adhered onto the surface of either the master medium 3 or the slave medium 2, when a pressure for allowing the master medium 3 and the slave medium 2 to be brought into close contact with each other is applied thereto, a gap is created in the vicinity of the adhering substance P between the master medium 3 and the slave medium 2 because a pressing surface 5a of the pressing support member 5 is a flat rigid body, thus causing an insufficient contact. Due to the insufficient contact, in a wide signal missing range D having a roughly circular shape around the adhering substance P as a center, the magnetic pattern corresponding to a micro uneven pattern made of a magnetic substance of the surface of the master medium 3 cannot be transferred to the slave medium 2, leading to the occurrence of a degradation in transfer and signal missing. Particularly, the signal missing range D thus occurred has an area such that a ratio of a diameter of the range D to a diameter d of the adhering substance P is large. It has been found that the adhering substance P is mainly made of dust or fiber waste generated in the manufacturing process of the slave medium 2, which is adhered onto the surface of the slave medium 2.
The present invention was made with the above-described problems in mind. The object of the present invention is to provide a method of magnetically transferring information signals from a master medium to a slave medium, which is capable of improving signal quality by reducing a signal missing range during the magnetic transfer.
The magnetic transfer method of the present invention, which has solved the foregoing problems, is a magnetic transfer method, comprising the steps of: preparing a master medium bearing information signals; preparing a slave medium; allowing the master medium and the slave medium to be brought into close contact with each other; and applying a transferring magnetic field to the master medium and the slave medium, thus magnetically transferring the information signals from the master medium to the slave medium. The magnetic transfer method of the present invention is characterized in that a material having an elastic property is mounted on one surface of the slave medium opposite with the other surface thereof contacting the master medium, and a pressing support member is mounted on the material with a pressing surface thereof contacting the material, the elastic property being of such a nature to deform in accordance with a surface shape of the slave medium when a contact pressure is applied to the material, and to restore an original surface shape thereof when the slave medium is released from the master medium.
It is preferable that a Young""s modulus of the material having the elastic property be set in a range from 5.0xc3x9710xe2x88x925 Pa to less than 3.0xc3x971010 Pa. It is preferred that the applied pressure during magnetic transfer be set in a range from 9.8xc3x9710xe2x88x925 Pa to less than 4.9xc3x9710xe2x88x923 Pa. Moreover, it is desirable that a thickness of the material having the elastic property be set in a range from 0.1 mm to less than 6 mm.
In the foregoing magnetic transfer method, preferably, the slave medium is first subjected to DC magnetization in a tracking direction, and the slave medium is allowed to be in close contact with the master medium for use in magnetic transfer, in which a magnetic layer is formed in a micro uneven pattern corresponding to information signals magnetically transferred. A transferring magnetic field should be applied to the master medium and the slave medium in a direction approximately reverse to an initial DC magnetization direction for the slave medium. A servo signal is preferred as the foregoing information signal.
According to the present invention as described above, when the master medium bearing the information signals to be transferred and the slave medium are allowed to be brought into close contact with each other, and the transferring magnetic field is applied to the two mediums, thus transferring the information signal from the master medium to the slave medium, the material is allowed to be interposed between the back of the slave medium and the pressing surface of the pressing support member, which presses the slave medium against the master medium. In this case, the material has an elastic property to deform its surface shape in accordance with the surface shape of the slave medium when a contact pressure is applied to the material and to restore its original surface shape when the slave medium is released from the master medium. Thus, when a pressure is applied to the material, the material having the elastic property deforms to the shape of the adhering substance. Accordingly, it is possible to narrow a range where a gap is created between the master medium and the slave medium on the periphery of the adhering substance. Hence, an occurrence range of the signal missing can be narrowed, thus enabling the quality of the transfer signal to be enhanced.
The Young""s modulus of the material having the elastic property is set in a range from 5.0xc3x9710xe2x88x925 Pa to less than 3.0xc3x971010 Pa. When the Young""s modulus is less than 5.0xc3x9710xe2x88x925 Pa, the material having the elastic property deforms in accordance with the shape of the adhering substance. However, after releasing the applied pressure, the material having the elastic property does not restore its surface shape to the original shape. Therefore, the material cannot achieve a complete close contact of the master medium and the slave medium at the next time and subsequently. Moreover, when the Young""s modulus is 3.0xc3x971010 Pa or more, since the material having the elastic property does not adaptively deform to the shape of the adhering substance, a wide space is created on the periphery thereof. Furthermore, also in terms of the surface property of the slave medium and the durability of the master medium, it is preferable to set the Young""s modulus in the above-described range.
The applied pressure during the magnetic transfer is set in a range from 9.8xc3x9710xe2x88x925 Pa to less than 4.9xc3x9710xe2x88x923 Pa, and the thickness of the material having the elastic property is set in a range from 0.1 mm to less than 6 mm. Thus, a better magnetic transfer characteristic can be secured.